Field devices assume a special role in process technology. In the context of this application the term “field devices” refers to any type of measuring devices, for example fill level measuring devices, pressure measuring devices, switching acquisition measuring devices or temperature measuring devices, to name but a few examples. Various physical effects may be utilised for the purpose of acquisition. Measuring data acquisition can take place by means of radar radiation, ultrasound, vibration, guided microwave, time domain reflection (TDR), or capacitive effects. Most of the time, field devices that are measuring devices measure process variables such as for example pressures, fill levels or temperatures, in an industrial environment. These process variables provide information about the state of a material to be processed, and are thus important parameters that may make it possible to optimally control a production process. In the form of actuators, field devices may be used to exert a controlling influence on processes, and if need be to alter process variables.
When using field devices, the measurements or activities are carried out as closely as possible to the material to be processed, so as to obtain the best possible feedback. The materials to be measured can also include materials which, at least in the longer term, can have a negative effect on the field devices. For example, if measuring sensors are used in the processing of corrosive acids there may be a danger that the sensors may become corroded by exposure to the acids.
In applications in industrial plant that have very substantial energy requirements, as may for example be the case in smelting or metallurgical process plants, very considerable electromagnetic radiation may occur as a result of switching large currents. Such electromagnetic radiation may have a negative effect on the operation of measuring sensors.
Likewise, exposure of the electronics of measuring devices to splash water may impede the function of said electronics and reduce their service life.
It is thus common for sensors, and in particular for the associated sensor electronics, to be incorporated in housings that are designed to protect them from exposure to environmental influences.